Pairing grid-forming VSC filter topologies with voltage control structures

This paper focuses on the voltage control of grid-forming Voltage Source Converters (VSCs) connected to AC networks. The work aims to identify the best pairing between voltage control structures and usual ac filter topologies. The two filter topologies considered are the inductive (L) and the inductive-capacitive (LC) filter. The control structures studied are the Cascaded Control (CC, cascaded voltage and current loop) and the direct Voltage Control (VC, without current loop). To select the best control-filter pair, the following methodology is suggested. First, for each pair, a voltage control parameter sweeping methodology is developed to find suitable designs considering the following limits: minimum bandwidth, maximum converter voltage, point of connection voltage deviation and maximum current. Second, this action is repeated for different filter parameters and network Short-Circuit Ratios (SCRs). Finally, based of the obtained results, the most relevant control-filter pairs can be selected, prioritizing them according to the fulfilment of the defined limits. To conclude, time-domain simulations are carried out to validate pairing selection.